Method and device for controlling a die-sink erosion machine

ABSTRACT

A method and a device are for controlling multiple machining processes in a die-sink erosion machine with several identical or different electrodes (R 1 , R 2 , R 3 , R 4 ), whereby the machining sequence of the machining processes and the electrode used for each machining process are determined by providing the following criteria: a) predefining priorities of workpieces to be machined, of a group of machining procedures, of individual machining jobs (ARB), of work cycles (AZ) and/or work steps (AS) of a machining job; and/or (b) predefining the life span or wear limit of the electrodes used for the individual machining jobs, work cycles or work steps. The overall machining on the die-sink erosion machine is performed with consideration of the determined machining sequence.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application corresponds to German Patent ApplicationNo. 198 56 098.2, which was filed in Germany on Dec. 4, 1998, and theentire contents of which are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention at hand relates to a method for controlling anumber of machining processes on a die-sink erosion machine and a devicesuitable for this purpose.

[0004] 2. Description of Related Art

[0005] Such a die-sink erosion machine is used, among other purposes,for manufacturing casting molds with extremely high machining precision.Hereby a number of machining processes which themselves are divided intoseveral working steps and working cycles of different machining stagesor phases are performed on one or more workpieces. Depending on themachining phase, such as roughing or finishing, often differentelectrode categories, such as, for example, roughing or smoothingelectrodes, are used for performing these machining processes. If, inaddition, the geometry of the performed machining job changes, theelectrode must be exchanged in most cases also. This means thatdepending on the number, versatility, and quality requirements of themachining processes to be performed in a modern die-sink erosionmachine, the order of the work steps to be performed and the electrodesrequired in each case requires an exact specification that is stored ina control program of a numerical control of the die-sink erosionmachine.

[0006] When setting up the die-sink erosion machine for such a complexmachining job, the machine operator must set the control inputs in thecontrol device that determine which work-steps of a machining processmust be performed in which sequence with which electrode on whichworkpiece. Standard, state-of-the-art control processes of the initiallymentioned type require control inputs in the form of closed “programs”,so-called sequential control programs, for this purpose. Such a controlprogram specifies all control data in respect to machining, machiningfrequency, and electrode used for each point in time during the overallmachining. Given the multiple work steps in a complex machining ofseveral workpieces that must be performed and the different electrodesnecessary for this purpose, the machine operator easily loses track, sothat setup errors could occur that would result in an improper, but atleast uneconomical execution of the machining.

[0007] The state of the art indeed knows of methods for the so-calledobject-oriented programming of machine tools, for example from Prof. Dr.Ing. Eversheim, Dipl.-Ing. Lenhart, Objektorientiert Programmieren, in:Industrie-Anzeiger 82/1991, p. 38-40. In contrast to sequential controlprograms, program components are used here that can be reused over andover again for changing the control program. Hereby only anobject-oriented structure of the source program is suggested. But notool for creating certain machining sequences is made available to themachine operator.

OBJECTS AND SUMMARY

[0008] The invention at hand attempts to improve die-sink erosionmachines in respect to their user friendliness where the creation of newmachining sequences is concerned.

[0009] According to one aspect of the present invention, a methodcontrols multiple machining processes in a die-sink erosion machine withseveral identical or different electrodes, whereby the machiningsequence of the machining processes and the electrode used for eachmachining process are determined with consideration of the followingpredefined criteria: a) predefining priorities of workpieces to bemachined, of a group of machining jobs, of individual machining jobs, ofwork cycles and/or work steps of a machining job; and/or (b) predefiningthe life span or wear limit of the electrodes used for the individualmachining jobs, work cycles or work steps. The overall machining on thedie-sink erosion machine is performed with consideration of thedetermined machining sequence. To create the machining sequences, adevice according to one aspect of the invention for controlling thedie-sink erosion machine has, for example, a CNC controller: at leastone data memory for the permanent storing of data describing theelectrodes required for the respective machining processes; a userinterface for inputting the previously mentioned criteria fordetermining the machining sequence into the control device; and asequence generator that automatically generates the suitable machiningsequence for the performing the multiple machining processes based onsaid criteria and electrode data.

[0010] The invention therefore offers the machine operator a proven toolfor setting even complicated machining sequences on a die-sink erosionmachine in a relatively simple manner and short time. The creation ofthe sequence and therefore also of the control program and thesubsequent machining also takes into account tool wear, for example, bypredefining the tool life span as the maximum number of possible workcycles for each machining type, for example for roughing and smoothingcycles. Once the predefined wear limit of a tool is reached, a tooladministration or management system according to one aspect of theinvention preferably excludes the tool from further machining ordowngrades it to a different tool category, as will be described in moredetail below. In this way, the selection of the favorable machiningsequence according to the invention is based on the fact that theavailable electrode material is optimally used, i.e., each electrode isused for several machining processes with or without interruption untilits individual life span expires. Another outcome of predefiningsuitable machining priorities is also that a certain object will bemachined before another object is completed. It would be possible, forexample, that a certain workpiece would need to be machined with ahigher priority because a customer needs this workpiece immediately, ora specific, complicated machining job is moved ahead so that in the caseof a failure a workpiece which was already machined with great effort isnot lost. A specific predefining of priorities also makes it possible toperform several machining jobs in as little time as possible, and tominimize any traveling distances between machining jobs during which noerosion is possible as much as possible.

[0011] The method according to one aspect of the invention and thecorresponding device naturally can be transferred to other types ofmachine tools in which comparable wear symptoms of the used tools occurand/or similar machining priorities can be used.

[0012] The term “machining process” has been used in this document as ageneral term comprising all parts of the work performed on a die-sinkerosion machine. This includes the execution of a particular die-sinkwith a predefined die-sink geometry which is called a “machining job”.Each machining job is performed in several machining steps or phases,for example, in consecutive order, roughing, pre-smoothing, smoothing,and finishing. In each machining phase, a machining job again consistsof several work steps that may be combined into so-called work cycles.The term “machining sequence” therefore in general relates to the orderof the consecutively performed machining processes which, depending onthe type of machining process, may be the order of consecutivelyperformed machining jobs, work cycles of several machining jobs and/orwork steps in a work cycle of a certain machining job or combinations ofthese sequences.

[0013] An especially preferred embodiment of the method uses theso-called wear distribution strategy as a selection criterion forperforming several identical machining jobs. The individual machiningjobs are hereby not completed in their respective entirety, one afterthe other, but the consecutively performed machining processes areinstead distributed in such a way over several machining jobs that aneven distribution of the electrode wear over a certain number of workcycles and/or work steps of the multiple machining jobs is obtained. Itis known that a sinker electrode experiences electrode wear during themachining, which can be attributed to the electrophysical nature of theerosion process so that the sinker electrode wears after performing acertain number of work steps. Therefore, in order to maintain the mosthomogeneous machining quality possible for all machining jobs, it isadvantageous to perform all identical or equally ranked working steps ofmultiple machining jobs consecutively, for example, starting with allfirst work steps of the multiple machining jobs, then all second worksteps, etc., until all of the last work steps of the multiple machiningjobs have been performed.

[0014] In this connection, the multiple, identical machining jobs of awear distribution area are preferably performed consecutively in acertain order, for example 1-2-3-4, and after a first (1) or last (4)machining job are repeated in reverse order, i.e., 4-3-2-1, until allwork steps of the machining jobs have been performed. This embodiment ofthe wear distribution strategy avoids that one machining job is machinedwith privileges over another. As a result, the wear distributionstrategy makes it possible that all identical machining jobs are erodedequally well (or equally poorly). In the proposed embodiment, theelectrode quasi moves in “pendulum” fashion through the rows of equallyranked work steps of several machining jobs, from the first to the lastmachining job, from the last to the first, etc., until all work steps ofthe machining jobs have been completed (so-called pendulum method), sothat all machining jobs are completed very quickly.

[0015] It is also preferred that the maximum electrode wear of anelectrode is defined by the maximum number of work cycles or work stepsthat can be completed with this electrode, whereby this number at thesame time determines the group of work cycles or work steps in which thewear distribution strategy is used. In this manner, several work cyclesof a certain machining phase are, for example, combined into so-calledwear distribution groups which are in each case machined only with asingle electrode. After the wear distribution group has been completed,the life span of this electrode for the respective machining phase hasexpired. This ensures in a particularly clear manner that all electrodesare used completely.

[0016] The machining sequence in such a wear distribution group againcan be set according to the wishes of the machine operator, for example,preferably so that only selected areas of work steps in a group of workcycles are included in the wear distribution strategy. Only the last twowork steps in several work cycles of several machining jobs that werecombined into a wear distribution group are supposed to use an evendistribution of the wear of the used electrode, preferably in a pendulummethod, as mentioned above.

[0017] The information on the life span of an electrode of the die-sinkerosion machine, i.e., the maximum number of work cycles or work stepsof a certain machining phase for which an electrode can be used and thecurrent wear status can be obtained in various ways. In the case of adie-sink erosion machine in which several machining jobs, each of whichhas several work cycles, are performed consecutively, the maximumelectrode wear is preferably predefined for use in an electrodeadministration system using the maximum number of work cycles or worksteps that can be performed with one electrode, and the electrodeadministration system counts and registers the number of performed workcycles or work steps during the machining. The information regarding theelectrode life span makes it possible to set up an automatic electrodeadministration or electrode management system in the controller of thedie-sink erosion machine. If a certain electrode has reached thepredefined wear limit, it is automatically excluded by theadministration system from further machining or is assigned to anothermachining phase, i.e., to another electrode category for which thiselectrode can still be used. The entire electrode administration takesplace via an intelligent CNC controller of the machine.

[0018] It is preferred that the electrodes are described in theadministration system of the control device by way of a currentmachining status, whereby the latter is adapted during the course of themachining in relation to the electrode wear. The electrodeadministration according to the invention therefore monitors the wearstatus of the used electrodes which are, for example, available in anelectrode changer, and assigns to them storage status properties, suchas “usable”, “unusable” or “downgraded to roughing electrode”, etc.

[0019] To perform a machining sequence, the controller also needsdetailed information about the electrodes used in each work step of themachining sequence. According to an especially preferred exemplaryembodiment, the data for describing the electrodes in the control deviceare divided for this purpose into the following groups and administeredaccordingly:

[0020] abstract electrode data for describing a standard electrode (V1,V2) that contain information for performing a certain machining process;and,

[0021] specific electrode data for correcting and/or adapting theabstract electrode data to the actually used electrode (R1, R2) or tomachine-specific characteristics,

[0022] whereby the electrode description is obtained by linking theabstract electrode data with the specific electrode data.

[0023] The abstract electrode data already contain all essentialinformation about the electrode(s) planned for performing a specific(individual) machining job in a specific type of machining. This is adescription of standard or specified electrodes required for performinga specific, desired machining job, whereby this abstract descriptionalso contains all machining-specific information of the electrode, forexample the basic electrode geometry, the basic electrode shape, theelectrode material, the electrode category, for example whether it is aroughing or a smoothing electrode. The specific electrode data thencontain only the correction data, for example in respect to the exactdimension of the actually used electrode, such as the actual, smallerthan specified size which may differ from the (assumed) smaller thanspecified size of the prescribed tool, as well as machine-specific data,such as, for example, the exact chucking position of the electrodes, thecurrent position in an electrode magazine for an automatic electrodechange and/or the current wear status of the actually used electrode, asit is registered in the above mentioned administration system. The ideais therefore to generalize the electrode description, i.e., to abstractit in the description of a standard tool independently from the actuallyencountered situation in the die-sink erosion machine and the realelectrodes used, so that the electrode description can already beperformed before the actual machining, outside the workshop. It ispreferred that an intelligent data generator automatically determinesthe machining sequence with the technology and process parameters ofindividual work steps of the desired machining job on the basis of theabstract electrode data together with the sequence selection criteriaaccording to the invention and geometrical data and technology andprocess parameter sets available in databases.

[0024] Another criterion for selecting and determining the machiningsequence is the predefining of priorities. There are different preferredpossibilities for adapting the desired machining sequence to thecorresponding circumstances for this purpose.

[0025] In one embodiment, the machining sequence is determined as amatter of priority by the priorities assigned to the workpieces, groupsof machining jobs, and individual machining jobs within a group(“workpiece” strategy). The machining job with the highest priority inthe group is hereby performed first on the workpiece with the highestpriority, from the first work step to the last one. Hereby no weardistribution is employed for the used electrode, since only onemachining job is always performed after another, i.e., the machiningprocesses are not distributed over several machining jobs. It ispreferred that with the “workpiece” strategy the electrode wear isactively counted, whereby, for example, the respective electrode isassigned the storage status “unusable” in the electrode administrationafter the wear limit has been reached.

[0026] In another embodiment, the machining sequence of machining jobsperformed in several machining steps or phases, such as, initially,roughing, then pre-smoothing, etc., and where in each machining phasethe work steps of a single machining job in each case have been combinedinto work cycles, is determined as a matter of priority by the fact thatall work steps of all machining jobs are performed in the predefinedhierarchy of the machining phases. For example, in the case of severaldie-sinks, first all work steps of the roughing cycles, then all worksteps of the pre-smoothing cycles, etc., are performed. Depending on thedesired machining quality, this strategy also distinguishes: (a) the“phase” strategy, in which all work steps in each machining phase areperformed consecutively from start to finish of a machining job, thenall work steps of the next machining job are performed from start tofinish, etc., until the last machining job of the same machining phasehas been performed; and (b) the “phase 0” strategy, in which initiallyall first work steps of several machining jobs of the same machiningphase are performed, and then, based on the last machining completed,the remaining work steps of the machining jobs are completed asdescribed for the “phase” strategy. Because these “phase” and “phase 0”strategies distribute the machining sequence in a specific machiningphase over several machining jobs, it is particularly advantageous toadditionally use the above described wear distribution strategy here.For example, given a specific wear limit of an electrode type, such asthe roughing electrode, a wear distribution group consisting of, forexample, four roughing cycles distributed over four identical machiningjobs, is formed. Within this wear distribution group it is also possibleto limit the wear distribution function only to the first two work stepsper cycle, and to use the progression of the “phase 0” strategy for theremainder.

[0027] Other possibly advantageous embodiments include those in whichthe machining sequence is assigned as a matter of priority according tothe priority of a workpiece and the strategy specified for the workpiece(“piece” strategy), or as a matter of priority according to thepriorities assigned to the individual work steps (“work step” strategy).The latter makes it, for example, possible to set the machining sequenceto the lowest level of the machining processes, so that the machineoperator is also able to predefine individual sequences of work stepsfor the control device.

[0028] It is also especially preferred that combinations of thementioned strategies, such as of the “workpiece” strategy and the“phase” or “phase 0” strategy are used.

[0029] In a first combination embodiment, the machining sequence is as amatter of priority determined by the “workpiece” strategy, whereby theworkpieces, groups or machining jobs are completed with same priorityusing the “phase” or “phase 0” strategy (so-called “workpiece-phase” or“workpiece-phase 0” strategy). This combined strategy is suitable inparticular in connection with a “cascade-type” downgrading of the usedelectrodes, whereby those electrodes used, for example, in a work cycleof a high phase, for example a smoothing cycle of the machining job withthe highest priority, can still be used for machining jobs of lowerpriority after the expiration of their life span for one or more workcycles of a lower phase, for example, a roughing cycle. If, in addition,a wear distribution strategy is desired for the work cycles to beperformed, the former naturally can be set for machining jobs with thesame priority.

[0030] In a second combination embodiment (“phase-workpiece” or “phase0-workpiece” strategy), the machining sequence is influenced accordingto the “phase” or “phase 0” strategy to the extent that the sequence ofwork steps and possibly the order of the division of the weardistribution groups take into account the priority of the machining jobsaccording to the “workpiece” strategy.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The following describes preferred exemplary embodiment of theinvention in reference to the enclosed drawings. This will showadditional advantages and characteristics of the invention. In thedrawing:

[0032]FIG. 1 shows a schematic top view of a casting mold with severaldie-sinks that can be produced with a die-sink erosion machine;

[0033]FIGS. 2a,b show a schematic view of an electrode changer in adie-sink erosion machine with several sinker electrodes arranged inelectrode holders;

[0034]FIG. 3 shows a schematic view of a machining sequence forperforming several machining jobs with different electrodes;

[0035]FIGS. 4a,b show a schematic view of the object structure ofvarious electrode families and associated real or virtual electrodes foruse in the machining sequence according to FIG. 3;

[0036]FIG. 5 shows a schematic view of another example of a machiningsequence according to the invention;

[0037]FIG. 6 shows a schematic view of another example of a machiningsequence according to the invention;

[0038]FIG. 7 shows a schematic view of another example of a machiningsequence according to the invention;

[0039]FIG. 8 shows a schematic view of another example of a machiningsequence according to the invention;

[0040]FIG. 9 shows a schematic view of another example of a machiningsequence according to the invention; and,

[0041]FIG. 10 shows a schematic view of a control system for generatingand executing machining sequences for performing one or more workpiecemachining jobs.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The invented control and electrode administration concept of adie-sink erosion machine will now be described in reference to theexample of preferred machining sequences and their associatedstrategies. But these should not be understood to limit the invention.Depending on the selection and weighting of the selection criteriadescribed initially, an almost unlimited number of different machiningsequences with associated description of the technology can be created.

[0043] In connection with FIGS. 1, 2a,b, and 3, a first example of theinvented creation of a certain machining sequence for a workpiece withseveral machining jobs, i.e., die-sinks having an identical or differentgeometry, is explained. For example, a suitable casting mold for theserial production of a rubber damper element for a differential couplingis supposed to be produced on a die-sink erosion machine. FIG. 1 shows aworkpiece 10 that has the final shape of a mold half of such a castingmold. This means that the die-sink erosion machine will be used to makeeight die-sinks A to H in the workpiece, offset from each other by 45°each, as well as an annular die-sink I. Two mold halves must be producedhereby, i.e., the identical arrangement of die-sinks A to I on anotherworkpiece 10′ (not shown). The workpiece 10 is here mounted on a pallet12 that is positioned on the tool table of the die-sink erosion machine.

[0044] The machining processes planned for the workpiece 10 thereforeinclude a total of nine machining jobs, each of which requires at leasttwo machining phases, i.e., a roughing and a subsequent pre-smoothingphase. Each phase again comprises several work steps for each machiningjob, where these work steps are again combined into so-called workcycles. The selection of the machining sequence, i.e., the order of thephases, of the work steps of a work cycle to be completed, and the workcycles per phase, depends on the selection of the machining strategywhich again depends, among other things, on the number of required andavailable sinker electrodes of the different categories and on theirlife span. In the case at hand, the machine operator is primarilyconcerned with performing the total machining job on the workpiece 10 asquickly as possible, i.e., to avoid periods of standstill, and toutilize the available electrodes as best as possible, i.e., to use eachof them to its wear limit. The number of available electrodes islimited, for example, by the storage capacity of an electrode changer ofthe die-sink erosion machine, where this electrode changer changes theused electrodes several times during the course of the overall machiningjob of a workpiece. FIG. 2a and 2 b show a section of such an electrodechanger with a total of twelve electrode holders 16 in positions P1 toP12. Several electrodes required for the machining of the workpiece 10in FIG. 1 are so wide that they require more than one holder space inthe electrode changer. This means that the shown electrode changer hasonly just space for a total of ten electrodes R1, R2, . . . R10 requiredfor producing the two mold halves of FIG. 1. An optimum utilization ofthe electrode material is ensured if five sinker electrodes are used forthe total machining of one mold half according to FIG. 1, i.e., threeelectrodes for producing the actual damper element die-sinks A to H, andtwo electrodes for the die-sink I of the connecting ring.

[0045] The controller of the die-sink erosion machine has an electrodeadministration system that records the current wear status of eachelectrode and changes it during the machining, if required. For thispurpose, the life span of an electrode is predefined in theadministration system, i.e., in the form of the maximum number of workcycles that can be performed for each phase of a special machining job.The electrode administration system is also provided with a counterdevice that continuously counts the number of work cycles completed andstores them in a memory of the administration system. If a specificelectrode now reaches the maximum permissible number of work cycles, theelectrode is excluded from the administration system either from furtheruse, i.e., it is assigned the storage status “unusable”, or if possiblethe electrode is downgraded to another electrode category for use inanother machining phase. In the latter case, the machine operatoractivates the option “Electrode movement with downgrading” in theelectrode administration system, hereby setting the control device sothat the pre-smoothing electrodes are automatically downgraded toroughing electrodes once they reach their wear limit and are used duringthe further course of the machining as such.

[0046] The following criteria are used for the additional determinationof the machining sequence in order to produce the mentioned mold parts:first all first work steps of the roughing cycles of machining jobs A toH should be performed, so that the initially described “phase 0”strategy is selected for this. Then the roughing cycles should be erodedas quickly as possible, so that the control device is set to the “phase”strategy. During the pre-smoothing cycles which represent the lastmachining phase in this case, an even distribution of the electrode wearover the different machining jobs A to H is desired in order to maintaina homogeneous machining quality. The machine operator therefore selectsthe previously described wear distribution strategy and sets the controldevice to the “Wear distribution over entire machining phase” option. Inthe area of the wear distribution, the inevitable electrode wear is thendistributed evenly over equally ranked work steps of several machiningjobs in the same phase. The machine operator also predefines the lifespan or wear limit by setting the maximum permissible number of workcycles per machining phase in the electrode administration system. Thisnumber at the same time determines the size of that group of work cyclesof a phase in which the wear distribution strategy will be used(so-called wear distribution group). Each wear distribution group ismachined with a single electrode of the associated category; after thegroup has been completed, the electrode has at least for this phasereached its wear limit. Using a pre-smoothing electrode, at least fourpre-smoothing cycles can be performed with wear distribution, forexample; after this, the electrode has reached its wear limit as apre-smoothing electrode. The same electrode theoretically now can beused also for performing four or more roughing cycles, i.e., as aroughing electrode. After this, the electrode is generally no longerusable.

[0047] The specification for the machining sequence for performing thecircular die-sink I in FIG. 1 is accomplished in a similar manner. Thedie-sink I should be performed with a single roughing electrode and asingle pre-smoothing electrode.

[0048] Using these presets, the control device automatically generatesthe entire sequence of the work cycles for producing the eight damperelement die-sinks A to H and the circular die-sink I in the workpiece 10according to FIG. 1, and also determines which electrodes to use in eachcase. FIG. 3 shows a schematic of this machining sequence. Die-sinks Ato I each have been designated with ARB A to ARB I. A roughing cycle(machining phase 1) and a pre-smoothing cycle (machining phase 2), eachconsisting of three or, respectively, four work steps AS has beenprovided for each of the die-sinks A to H. Based on the above predefinedwear limit of a maximum of four work cycles AZ for the roughing andpre-smoothing electrodes, the roughing and pre-smoothing cycles are ineach case combined into groups GR1 to GR4 of four work cycles AZ, eachof which is machined with a single electrode.

[0049] According to the sequence in FIG. 3, the control device firstgets an electrode R1 from position P9 in the electrode changer of FIG.2. This is used to first complete the roughing cycles of die-sinks A, B,C, and D in the first group GR1, i.e., according to the predefined“phase 0” strategy, first all first work steps AS of the four die-sinksA, B, C, and D, and then the remaining work steps AS are performed,whereby in the order of the die-sinks D, C, B, and A the second andthird work steps AS of each work cycle AZ are consecutively completedbefore the next die-sink is further machined. After completion of thefirst work cycle group GR1, the electrode R1 is again placed back intothe electrode changer and is automatically exchanged for an electrode R2from position P10. At the same time, the electrode administration systemof the controller stores the status of the electrode R1 as “unusable”.The electrode administration system obtains further information aboutthe wear status of the remaining electrodes via the predefining of themaximum number of work cycles that can be performed and the continuouscounting of already performed work cycles.

[0050] The new electrode R2 is then used to perform the pre-smoothingcycles of die-sinks A, B, C, and D in group GR3, i.e., according to theset wear distribution strategy by using the so-called pendulum method inwhich first all first work steps AS of die-sinks A, B, C, and D, thenall second work steps AS are completed in reverse order D, C, B, A,etc., until the last work steps AS in group GR3 are performed. Nowelectrode R2, which had been initially used as a pre-smoothingelectrode, is downgraded by the electrode administration to the categoryof a roughing electrode since it has already performed the four maximumpermissible pre-smoothing cycles. Electrode R2 is now used again as aroughing electrode for machining the die-sinks E, F, G, and H, i.e.,according to the “phase 0” strategy applicable for the roughing cycle,which means according to the same machining sequence as group GR1. Aftercompleting the work cycle group GR2, the electrode R2 now has alsoreached its wear limit for a roughing electrode and is thereforedowngraded by the electrode administration as generally “unusable”. Thepre-smoothing cycles of die-sinks E, F, G, and H are finally performedwith a new electrode R3 from the electrode changer. Then electrode R3 isalso downgraded; theoretically it would still be suitable as a roughingelectrode for machining another tool.

[0051] After all damper element die-sinks A to H have been eroded, thecontrol device gets another electrode R5 from position P1 in theelectrode changer and performs the intended roughing cycle according tothe sequence in FIG. 3, and following this performs the pre-smoothingcycle for die-sink I with another electrode R6.

[0052] To perform such a machining sequence, the CNC machine controlleralso requires control inputs in respect to the used electrode types,geometry data of the die-sinks, the quality goal and machining speed, aswell as the process and technology parameters, such as erosion current,pulse shape, pulse frequency, flushing data, etc. Together with theabove-mentioned predefinitions for the machining sequence, these dataare also used to determine the sequence of the individual work stepsusing the respective technology and process data. The invention at handalso provides the machine operator with a tool for more efficientlydescribing the various electrode categories. For this purpose, differentelectrode categories for performing a specific machining job, forexample one of the die-sinks A to I in FIG. 1, are combined into anelectrode family and are considered as an object in an object-orientedstructure of the die-sink erosion machine controller. Accordingly, thesame electrode family then includes all those electrodes that have atleast the same basic geometry and a predefined smaller than specifiedsize that is able to achieve the same final dimensions. An object of theelectrode family can be used for several (identical) machining jobs,i.e., for all machining jobs in which a corresponding die-sink geometryshould be achieved.

[0053] According to the invention, three data areas are provided in thecontroller for describing the electrodes:

[0054] a) Data of the electrode family (so-called family data) Thefamily data contain information applicable for all electrodes of aspecific electrode family. This includes essentially information about:electrode material (the choice of the electrode material determines thepaired materials (electrode/ workpiece) of the erosion, so that thecontroller will be able to automatically determine the matchingtechnology parameters. But if the members of an electrode family aremade of different materials, the electrodes differing from the materialdata defined on the family level must be specified on a subsequent datalevel); as well as basic electrode geometry, i.e., information about thebasic shape (for example, prismatic, lamella-shaped, pointed, orstandard shapes), and information about the basic geometric dimensions.

[0055] b) Abstract electrode data (data of so-called virtual electrodes)The abstract electrode data contain information about virtual electrodesplanned for performing a specific machining job in a specific machiningtype or phase. This is a description of a standard or specifiedelectrode for performing the specific machining job, which alreadycontains all essential machining-specific information. The abstractelectrode data include, for example, information about: electrodecategory for a specific machining type, for example, roughing,pre-smoothing, smoothing, or finishing electrode; number of plannedvirtual electrodes per machining type; theoretical smaller thanspecified size or standard smaller than specified size (smaller thanspecified size=diameter of final mold minus diameter of electrode) whichmay slightly differ from the smaller than specified size of the actuallyused (real) electrode (the controller automatically determines the pulsefrequency and number of pulses per electrode, along with the requiredquality goal, from the number of electrodes and the expected, smallerthan specified size); and the electrode life span expressed as thenumber of maximum permissible work cycles per machining phase.

[0056] c) specific electrode data (data of so-called real electrodes)These are essentially correction data in contrast to the abstractelectrode data of the virtual electrodes for adapting the actually usedreal electrodes to a (single or multiple) performing of a specificmachining job. These correction data on the one hand relate toelectrode-specific properties, for example the actual smaller thanspecified size of the used electrode or information about the currentelectrode wear status, and on the other hand to machine-specificproperties, such as information about the mode of the electrode changeand position of the electrode on an automatic electrode changer orrobot, information about the installation of the electrode in thedie-sink erosion machine for example, whether it is installed on theelectrode head or on the tool table correction values of the electrodeposition in order to determine the exact zero point of the electrode inrelation to the zero point of the electrode head, etc.

[0057] The total information about an electrode to be used for aspecific work cycle is obtained from the sum of the specific electrodedata of the real electrode, the abstract electrode data of the virtualelectrode, and the superordinate family data. This way of dividing andgrouping the electrode description promotes the generation of variousmachining sequences, since it permits a flexible and quick adaptation ofthe electrode description to a changed machining sequence and theelectrodes required for this, for example, new electrodes. If, forexample, a new real electrode is used which is positioned in a newposition in the electrode changer, it is sufficient to only input thereal data of this electrode into the controller and link them with thealready existing virtual data of the desired machining type.

[0058]FIG. 4a and 4 b show the data structure of the electrodes as theyare used for the machining sequence in FIG. 3, i.e., at the beginning ofmachining. Of the four electrode families in FIG. 4a, only the electrodefamilies Fam. 1 and Fam. 2 are hereby relevant. In electrode familyFam.1, the roughing electrode used for work cycle group GR1 isdetermined by the assignment R1, V1; the two pre-smoothing electrodesfor work cycle groups GR3 and GR4 are based on the combination of thedata of the real and virtual electrodes R2, V2, and R3, V2. The roughingand pre-smoothing electrode for performing the machining job I arefurthermore defined by the data combination R5, V4 or, respectively, R6,V5. Within the framework of the object-oriented structure of the entirecontroller of the die-sink erosion machine, an electrode family Fam. 1and Fam. 2 have been assigned another superordinate “family group”object. As a result, the measures established for the family group applygenerally also for all electrode families Fam. 1 to Fam. 4.

[0059]FIG. 4b furthermore shows the above mentioned downgrading ofelectrode R2 during the course of the machining sequence of FIG. 3. Thereal electrode R2 there is defined first by the data combination R2, V2in the electrode family Fam. 1 as a pre-smoothing electrode ∇∇. Afterits life span has expired (as determined in the data of virtualelectrode V2), R2 is downgraded to a roughing electrode V. The totaldescription as a roughing electrode is simply obtained by assigning toit the data of the already existing virtual electrode V1 which accordingto the invention already contains all information for performing aroughing process.

[0060]FIG. 5 to 9 show further examples of machining sequences generatedin accordance with the criteria according to the invention.

[0061] The machining sequence with five electrodes R1 to R5 according toFIG. 5 resembles the one in FIG. 3. Here too the “phase 0” strategy forperforming four machining jobs ARB 1 to ARB 4 is predefined in thecontrol device. With this, the first work steps of consecutive workcycles of machining jobs ARB 1 to ARB 4 will always be performed firstin each phase 1, 2, and 3. However, the following settings have beenselected as criteria for the electrode life span and wear distributionof the electrodes: For phase 1 (roughing), a wear limit of a maximum offour smoothing cycles has been predefined, whereby the even weardistribution is only desired for the last two work steps of therespective work cycles; in phase 2 (pre-smoothing), a maximum of threecycles are predefined for the pre-smoothing electrode, whereby the evenwear distribution should be performed for all work cycles within thewear distribution groups; and in phase 3 (smoothing), a maximum of twosmoothing cycles are predefined per electrode, whereby the weardistribution is blocked during the last three work steps of therespective work cycles. Based on these sequence predefinitions, thecontrol device generates the machining sequence shown in FIG. 5, wherebythe electrode administration automatically performs an electrode changeat the points symbolized by a square box.

[0062] The machining sequence shown in FIG. 6 is in so far comparable tothe one in FIG. 5, in that the same setting for the electrode life spansand wear distribution has been selected there, and the first work stepsof the machining jobs also are always performed consecutively accordingto the “phase 0” strategy. However, jobs ARB 1 to ARB 4 here aresupposed to be performed with a priority that incrementally decreasesfrom ARB 4 to ARB 1, so that the machine operator here has set thepriority strategy “phase 0-workpiece”. In contrast to the purely “phase0” strategy in FIG. 5, the work steps are then performed in the weardistribution groups in the order of the priorities of the machiningjobs, i.e., from ARB 4 to ARB 1. The wear distribution groups are alsodivided in each phase in the order of the priorities of the machiningjobs.

[0063] The machining sequence with electrodes R1 to R7 shown in FIG. 7is also based on the same life span and wear distribution setting as inthe machining sequences in FIG. 5 and 6. The difference, however, is thepredefining of priorities of the machining jobs, i.e., the priorityperformance of machining job ARB 4 (priority: 1) before the othermachining jobs ARB 1 to ARB 3 (priority: 2). The latter machining jobsARB 1 to ARB 3 with the same priority should be completed as specifiedin the machining sequence in FIG. 5. The setting of the machiningsequence therefore is based on the “workpiece-phase 0” strategy,according to which all work cycles of phases 1 to 3 of the prioritymachining job ARB 4 are performed, and then the remaining machining jobsARB 1 to ARB 3 are completed according to the “phase 0” strategy withthe set wear distribution (cf. FIG. 5).

[0064] Finally, FIG. 8 and 9 show machining sequences for performingdifferent machining jobs ARB 1 to ARB 4. The wear distribution is notset here for these sequences. The machining sequence in FIG. 8 is basedon the setting of the “phase” strategy, and the sequence in FIG. 9 onthe “phase 0” strategy.

[0065] The control device according to the invention is based on a CNCcontrol. FIG. 10 shows a schematic of a control system 20 of a CNCcontroller of the die-sink erosion machine for generating and executingmachining sequences for performing various machining jobs on a workpiece10. The control system 20 has an interpolator 22 that controls therelative movement between workpiece and sinker electrode necessary forthe workpiece machining. For this purpose, a drive is provided that is,for example, coupled with the tool table, is movable in x, y, and z mainaxis direction, and receives the control signals of the interpolator 22.The control system 20 requires a control program which, in addition tothe positional data of the workpiece(s), geometry and contour data ofthe desired die-sinks, also contains technology data, such as machiningprecision, roughness, etc., and process parameter data, such as erosioncurrent, pulse current, pulse frequency, flushing data, etc., i.e., foreach work step of a predefined machining sequence. The die-sink erosionmachine's control system 20 according to the invention automaticallygenerates the machining sequence of the work steps along with theassociated control data. For this purpose, the control system 20 has agraphical interface (not shown) through which predefined settings forcreating the machining sequence, such as machining priorities, electrodelife span, wear distribution strategies are selected and set incorresponding windows. The data of the virtual electrodes (abstractelectrode data) are also stored in memory 24, and the data of the realelectrodes (specific electrode data) are stored in memory 25 of controlsystem 20. The geometry and contour data of various machining jobs arefurthermore stored in memory 28, and various technology and processparameter data sets for performing the machining jobs are stored indatabases 30 and 31. An intelligent sequence and data generator 26 now,on the basis of the predefined sequence specifications, the data of thevirtual electrodes from memory 24, the geometry data from memory 28, andthe technology and process data from databases 30, 31 automaticallydetermines a specific sequence of work steps to be performed with therespective technology and process parameter data. This assignment stepis shown schematically in FIG. 5 with the light arrows.

[0066] The CNC control of the die-sink erosion machine also has anelectrode administration unit (33) for monitoring the electrode lifespan and for excluding or downgrading an expired electrode in thepreviously described manner.

[0067] At the moment the work steps defined in this manner are performed(cf. dark arrows in FIG. 5), the interpolator 22 accesses the real datastored in memory 25 and reads the data for controlling the electrodemovement. The data of the real electrodes are hereby integrated ascorrection values into the already defined work steps: the correctionvalues, for example, determine the zero point position of the realelectrodes related to the zero point of the electrode head; the actualsmaller than specified size of the electrodes is used to control theplanetary movements.

[0068] The present invention has been described with reference to apreferred embodiment. However, it will be readily apparent to thoseskilled in the art that it is possible to embody the invention inspecific forms other than as described above without departing from thespirit of the invention. The exemplary embodiment is illustrative andshould not be considered restrictive in any way. The scope of theinvention is given by the appended claims, rather than the precedingdescription, and all variations and equivalents which fall within therange of the claims are intended to be embraced therein.

What is claimed is:
 1. A method for controlling multiple machiningprocesses in a die-sink erosion machine with several identical ordifferent electrodes, comprising the steps of: determining a machiningsequence of the machining processes and the electrode used for eachmachining process with consideration of the following predefinedcriteria: a) predefined priorities of workpieces to be machined, of agroup of machining jobs, of individual machining jobs, of work cyclesand/or work steps of a machining job; and/or b) predefined life span ofthe electrodes used for the individual machining jobs, work cycles orwork steps; and performing the determined machining sequence of themachining processes.
 2. The method as claimed in claim 1, wherein in thecase of several identical machining jobs, the machining processes aredistributed in such a way over several machining jobs that an evendistribution of the electrode wear over a specific number of work cyclesand/or work steps of the multiple machining jobs is obtained.
 3. Themethod as claimed in claim 2, wherein the multiple, identical machiningjobs of a wear distribution area are performed consecutively in acertain order, and, after a first or last machining job, are repeated inreverse order until all work steps of the machining jobs have beencompleted.
 4. The method as claimed in claim 2, wherein the maximumelectrode wear is predefined by the maximum number of work cycles orwork steps that can be completed with this electrode, whereby thisnumber at the same time determines the group(s) of work cycles or worksteps in which the wear distribution strategy is used.
 5. The method asclaimed in claim 4, wherein within a group of work cycles only selectedparts of work steps are subject to the wear distribution strategy. 6.The method as claimed in claim 1, wherein during the machining thenumber of completed work cycles or work steps is counted and registered,and that a specific electrode, after reaching the predefined maximumelectrode wear, is excluded from further machining or downgraded toanother electrode category.
 7. The method as claimed in claim 6, whereinthe electrodes are described in an administration system of the controldevice with a current machining status, whereby this status is adaptedin relation to the electrode wear.
 8. The method as claimed in claim 1,wherein data for describing the electrodes are divided in the controldevice into: abstract electrode data describing a standard electrodethat contain information for performing a certain machining process; andspecific electrode data for conforming the abstract electrode data tothe actually used electrode or to machine-specific characteristics,whereby an electrode description is obtained by linking the abstractelectrode data with the specific electrode data.
 9. The method asclaimed in claim 8, wherein for a sequence of work cycles, each havingdifferent work steps, an electrode is determined by combining theabstract electrode data with various selected specific electrode datawithin a specific machining job for each work cycle and/or each workstep.
 10. The method as claimed in claim 1, wherein the machiningsequence is determined as a matter of priority by the prioritiesassigned to the workpieces, groups of machining jobs, and individualmachining jobs within a group (the “workpiece strategy”).
 11. The methodas claimed in claim 1, wherein, the machining sequence of machining jobsare performed in several machining phases and in each machining phasethe work steps of a machining job are combined into work cycles, whereinthe machining sequence is determined as a matter of priority by the factthat all work steps of all machining jobs are performed in a predefinedhierarchy of the machining phases, whereby, a) in each machining phaseall work steps are performed from the beginning to the end of amachining job, then all work steps are performed from the beginning tothe end of the next machining job, etc., until the last machining job(the “phase 0 strategy”); or, b) in each machining phase first all firstwork steps of all machining jobs are performed, and then the remainingwork steps of the machining jobs are completed as under the phase 0strategy defined above in a).
 12. The method as claimed in claim 1,wherein the machining sequence is determined as a matter of priority bythe priority of a workpiece and a strategy predefined for the workpiece.13. The method as claimed in claim 1, wherein the machining sequence isdetermined as a matter of priority by the priorities assigned to theindividual work steps.
 14. The method as claimed in claim 10, whereinthe machining sequence is set as a matter of priority specified by the“workpiece” strategy, whereby the workpieces, groups or machining jobsare completed with same priority according to the “phase” or “phase 0”strategy.
 15. The method as claimed in claim 10, wherein the machiningsequence is according to the “phase” or “phase 0” strategy influenced tothe extent that the sequence of work steps and possibly the order of thedivision of the wear distribution groups take into account the priorityof the machining jobs according to the “workpiece” strategy.
 16. Adevice for controlling a die-sink erosion machine on which a number ofmachining processes with several identical or different electrodes areperformed, comprising: at least one data memory for permanently storingdata describing the electrodes which are required for the respectivemachining processes; a user interface for predefining priorities ofworkpieces to be machined, of a group of machining jobs, of individualmachining jobs, of work cycles and/or work steps of a machining job;and/or the life span of the electrodes used for the individual machiningjobs, work cycles or work steps in relation to the machining sequence ofthe machining processes; and, a sequence generator that automaticallygenerates a suitable machining sequence for performing the multiplemachining processes based on the predefined priorities and the electrodedata.
 17. The device as claimed according to claim 16, furthercomprising an administration system that registers the number of workcycles or work steps performed during the machining job with the sameelectrode, and excludes the electrode from further machining ordowngrades it to another electrode category after the maximum number ofpermissible work cycles or work steps has been reached.
 18. The deviceas claimed in claim 17, wherein the electrodes are described in a memoryof the administration system with a current machining status, wherebythis status is adapted in relation to the electrode wear.
 19. The deviceas claimed in claim 16, further comprising: a data memory for thepermanent storing of abstract tool data for describing a standard tool;a data memory for the permanent storing of specific tool data forconforming the abstract tool data to the actually used tool or tomachine-specific characteristics; and the user interface includes meansfor selecting specific tool data and linking the abstract tool data withthe selected specific tool data.
 20. The device as claimed in claim 19,further comprising: a data memory for geometry and contour data ofdifferent machining jobs; a data memory for technology and processparameter data for performing the machining jobs; whereby the sequencegenerator automatically generates the machining sequences with theassociated technology and process parameters based on machining sequencepresets, the abstract electrode data, the geometry and contour data, andthe technology and process parameter data.
 21. The device as claimed inclaim 19, further comprising an interpolator which reads the specificelectrode data from the data memory and uses them to correct the toolmovement.